Security system for vehicle navigation system and method of detecting identification code

Abstract

A vehicle navigation system with a security feature capable of detecting that the system has been removed from the vehicle, which uses only one memory for storing an anti-theft code. The navigation system is provided with a GPS receiver containing a clock outputting a time synchronized with present GPS time information, while receiving electric power from the vehicle battery, and returns the time to an initial preset time when not receiving power from the battery, and detects a present position of the vehicle by means of the present GPS time and position information. A CPU detects whether or not the time of the clock has returned to the initial time, an SRAM stores a preset identification code, and a controller requests input of an identification code when the CPU detects that the time of the clock has returned to the initial time, and compares the input identification code to the identification code stored in the SRAM, and operates in accordance with the result of the comparison.

What is claimed is: 
     
       1. A vehicle navigation system having a security feature, comprising: a receiver including a clock outputting a time synchronized to present, received time information, wherein the receiver is coupled to a battery of the vehicle and returns the time to a preset time when the receiver does not receive power from said battery;   a detector coupled to the clock which detects whether the time of said clock has returned to the preset time;   a nonvolatile memory which stores an identification code; and   a controller coupled to said detector and which requests input of an identification code from a user of the system when said detector detects that the time of said clock has returned to the preset time, and which compares the input identification code to the identification code stored in said memory, wherein said controller puts the system into a normal state if the codes match.   
     
     
       2. A navigation system as in claim 1, further comprising a second memory which stores a specific time of said clock; and wherein said detector compares a time output from said clock to the specific time stored in said second memory, and thereby detects whether the time of said clock has returned to the specific time.   
     
     
       3. A navigation system as in claim 1, wherein said controller compares said input identification code to the identification code stored in said memory, and puts the system into an abnormal state if the codes do not match. 
     
     
       4. A navigation system as in claim 1, wherein said controller compares the input identification code to the identification code stored in said memory, and if the codes do not match, allows the identification code to be input repetitively, with a limit of a preset number of times, and if the codes do not thereafter yet match, puts the system into an abnormal state. 
     
     
       5. A navigation system as in claim 2, wherein said second memory is included in said controller. 
     
     
       6. A navigation system having a security feature, comprising: a receiver including a clock outputting a time synchronized to present, received time information, wherein the receiver is coupled to a battery of the vehicle;   a detector coupled to the clock and which detects whether the time output from said clock has varied more than a specific time, thereby indicating that an abnormal security condition may have occurred;   a nonvolatile memory which stores a preset identification code;   a controller coupled to said detector and which requests input of an identification code from a user of the system when said detector detects that the time of said clock has varied more than said specific time, and compares the input identification code to the preset identification code stored in said memory, wherein said controller puts the system into a normal state if the codes match.   
     
     
       7. A navigation system as in claim 6, wherein said specific time is one of one year, one month, and one day. 
     
     
       8. A method of detecting an identification code in a vehicle navigation system having a security feature, comprising the steps of: storing an identification code in a nonvolatile fashion;   detecting whether a time of a clock has returned to a specific time, wherein said clock outputs a time synchronized to present, received time information, and wherein the clock is coupled to a battery of said vehicle and returns the time to the specific time when the clock is not coupled to said battery;   inputting an identification code from a user of the system upon detection that the time of said clock has returned to the specific time;   comparing the input identification code to the stored identification code; and   entering a normal processing state if the codes match.   
     
     
       9. A method as in claim 8, wherein the code is input repeatedly, with a limit of a specific number of times, if the codes do not initially match. 
     
     
       10. A method as in claim 8, wherein if the codes do not match entering a termination processing state. 
     
     
       11. A method of detecting an identification code in a vehicle navigation system having a security feature, comprising the steps of: storing an identification code in a nonvolatile fashion;   detecting whether a time of a clock has varied more than a specific time to thereby indicate that an abnormal security condition may have occurred, wherein said clock is in a receiver and outputs a time synchronized with present, received time information while the receiver is coupled to a vehicle battery;   inputting an identification code from a user of the system when it is detected that the time of said clock has varied more than a specific time;   comparing the input identification code to the stored identification code; and   entering a normal processing state if the codes match.   
     
     
       12. A method as in claim 11, wherein said specific time is one of one year, one month, and one day. 
     
     
       13. A vehicle navigation system having a security feature, comprising: a receiver including a clock outputting a time synchronized to present, received time information, wherein the receiver is coupled to a battery of said vehicle and the clock returns the time to a specific time when the receiver is not coupled to said battery;   a detector coupled to said receiver and which detects whether the time of said clock has returned to the specific time;   a nonvolatile memory which stores a preset anti-theft code; and   a controller coupled to said detector and which requests input of an anti-theft code from a user of the system when said detector detects that the time of said clock has returned to the specific time, and which compares the input anti-theft code to the stored anti-theft code and puts the system into a normal security state if the codes match.   
     
     
       14. A navigation system as in claim 13, further comprising: a second memory which stores a specific time of said clock; and wherein said detector compares a time output from said clock to the specific time stored in said second memory, and thereby detects whether the time of said clock has returned to the specific time.   
     
     
       15. A navigation system as in claim 13, wherein said controller detects a present position of the vehicle from information received by said receiver. 
     
     
       16. A navigation system as in claim 13, further comprising a sensor coupled to the controller and providing information as to movement of the vehicle, wherein said controller determines a present position of the vehicle using both information received by said receiver and information from said sensor. 
     
     
       17. A navigation system as in claim 13, wherein said controller compares said input anti-theft code to said anti theft code stored in said memory, and if the codes do not match, puts the system in an abnormal security state.